I can understand its all extremely confusing .... i have also been to
this stuff it took me 5 moths just to understand how everything worked
.....
my advice to you you is that you should atlest read about how mpeg 2
compression works .... mpeg4 , h264 and other compression are quiet
complex but at their core they work pretty much like mpeg 2 compression
atlest concern mpeg2 part in this book its bit out dated but you would
understand that how everything works
https://dl.dropboxusercontent.com/u/15671916/video%20compression/DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf
you dont need to have to go too deep to understand video
decoding/encoding ... ffmpeg library will do much for you ... just get
some of how mpeg 2 codec works
On 12/10/2013 12:14 PM, YIRAN LI wrote:
Hi friends,
I'm now checking a duration issue of a video file.
Here is some trace print out when file is opened, so we can know the
dts of last AVPacket is 167542, and the last frame time stamp =
167376, and coded_picture_num = 4013
Line 100: 00:00:33.384 MAIN rhbc73 process packet, Packet.dts = 0,
Packet.pts = -9223372036854775808 Line 101: 00:00:33.384 MAIN rhbc73
process packet, Packet.dts = 42, Packet.pts = -9223372036854775808
Line 102: 00:00:33.400 MAIN rhbc73 process packet, Packet.dts = 83,
Packet.pts = -9223372036854775808 Line 103: 00:00:33.400 MAIN rhbc73
process packet, Packet.dts = 125, Packet.pts = -9223372036854775808
Line 104: 00:00:33.400 MAIN rhbc73 process packet, Packet.dts = 167,
Packet.pts = -9223372036854775808 Line 105: 00:00:33.400 MAIN rhbc73
-- get a full frame, pFrame->pkt_dts = 0, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 0,
pFrame->coded_picture_number = 0 Line 107: 00:00:33.400 MAIN rhbc73
process packet, Packet.dts = 209, Packet.pts = -9223372036854775808
Line 108: 00:00:33.400 MAIN rhbc73 -- get a full frame,
pFrame->pkt_dts = 42, pFrame->pkt_pts = -9223372036854775808,
BestEffortTimeStamp = 42, pFrame->coded_picture_number = 1 Line 110:
00:00:33.400 MAIN rhbc73 process packet, Packet.dts = 250, Packet.pts
= -9223372036854775808 Line 111: 00:00:33.416 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 83, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 83,
pFrame->coded_picture_number = 2 Line 113: 00:00:33.416 MAIN rhbc73
process packet, Packet.dts = 292, Packet.pts = -9223372036854775808
Line 114: 00:00:33.416 MAIN rhbc73 -- get a full frame,
pFrame->pkt_dts = 125, pFrame->pkt_pts = -9223372036854775808,
BestEffortTimeStamp = 125, pFrame->coded_picture_number = 3 Line 116:
00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 334, Packet.pts
= -9223372036854775808 Line 117: 00:00:33.416 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 167, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 167,
pFrame->coded_picture_number = 4 Line 119: 00:00:33.416 MAIN rhbc73
process packet, Packet.dts = 375, Packet.pts = -9223372036854775808
Line 120: 00:00:33.416 MAIN rhbc73 -- get a full frame,
pFrame->pkt_dts = 209, pFrame->pkt_pts = -9223372036854775808,
BestEffortTimeStamp = 209, pFrame->coded_picture_number = 5 Line 122:
00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 417, Packet.pts
= -9223372036854775808 Line 123: 00:00:33.416 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 250, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 250,
pFrame->coded_picture_number = 6 Line 125: 00:00:33.416 MAIN rhbc73
process packet, Packet.dts = 459, Packet.pts = -9223372036854775808
Line 126: 00:00:33.416 MAIN rhbc73 -- get a full frame,
pFrame->pkt_dts = 292, pFrame->pkt_pts = -9223372036854775808,
BestEffortTimeStamp = 292, pFrame->coded_picture_number = 7 Line 128:
00:00:33.416 MAIN rhbc73 process packet, Packet.dts = 501, Packet.pts
= -9223372036854775808 Line 129: 00:00:33.416 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 334, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 334,
pFrame->coded_picture_number = 8 Line 131: 00:00:33.416 MAIN rhbc73
process packet, Packet.dts = 542, Packet.pts = -9223372036854775808
Line 132: 00:00:33.416 MAIN rhbc73 -- get a full frame,
pFrame->pkt_dts = 375, pFrame->pkt_pts = -9223372036854775808,
BestEffortTimeStamp = 375, pFrame->coded_picture_number = 9 Line
12134: 00:00:51.168 MAIN rhbc73 process packet, Packet.dts = 167417,
Packet.pts = -9223372036854775808 Line 12135: 00:00:51.168 MAIN rhbc73
-- get a full frame, pFrame->pkt_dts = 167250, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 167250,
pFrame->coded_picture_number = 4010 Line 12137: 00:00:51.168 MAIN
rhbc73 process packet, Packet.dts = 167459, Packet.pts =
-9223372036854775808 Line 12138: 00:00:51.168 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 167292, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 167292,
pFrame->coded_picture_number = 4011 Line 12140: 00:00:51.168 MAIN
rhbc73 process packet, Packet.dts = 167501, Packet.pts =
-9223372036854775808 Line 12141: 00:00:51.168 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 167334, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 167334,
pFrame->coded_picture_number = 4012 Line 12143: 00:00:51.184 MAIN
rhbc73 process packet, Packet.dts = 167542, Packet.pts =
-9223372036854775808 Line 12144: 00:00:51.184 MAIN rhbc73 -- get a
full frame, pFrame->pkt_dts = 167376, pFrame->pkt_pts =
-9223372036854775808, BestEffortTimeStamp = 167376,
pFrame->coded_picture_number = 4013
But when I check the file using ffprobe -show_frames -select_streams v
input I could see
[FRAME]
media_type=video
key_frame=0
pkt_pts=N/A
pkt_pts_time=N/A
pkt_dts=167501
pkt_dts_time=167.501000
pkt_duration=N/A
pkt_duration_time=N/A
pkt_pos=103794518
pkt_size=74
width=1920
height=1080
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=P
coded_picture_number=4016
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
[/FRAME]
[FRAME]
media_type=video
key_frame=0
pkt_pts=N/A
pkt_pts_time=N/A
pkt_dts=167542
pkt_dts_time=167.542000
pkt_duration=N/A
pkt_duration_time=N/A
pkt_pos=103794920
pkt_size=74
width=1920
height=1080
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=P
coded_picture_number=4017
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
[/FRAME]
the ffprobe and ffmpeg libs were built from same latest source, so I'd
like to know why ffprobe could dump a last frame of timestamp 167542
but av_read_frame + avcodec_decode_video2
couldn't
Thanks
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